Re: [dpdk-dev] [PATCH v6 07/19] vhost: add number of fds to vhost-user messages and use it

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 10/12/2018 10:45 AM, Maxime Coquelin wrote:
> 
> 
> On 10/12/2018 10:43 AM, Maxime Coquelin wrote:
>>
>>
>> On 10/11/2018 05:59 PM, Ilya Maximets wrote:
>>> On 11.10.2018 12:24, Maxime Coquelin wrote:
>>>> As soon as some ancillary data (fds) are received, it is copied
>>>> without checking its length.
>>>>
>>>> This patch adds the number of fds received to the message,
>>>> which is set in read_vhost_message().
>>>>
>>>> This is preliminary work to support sending fds to Qemu.
>>>>
>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>>>> ---
>>>>   lib/librte_vhost/socket.c     | 25 ++++++++++++++++++++-----
>>>>   lib/librte_vhost/vhost_user.c |  2 +-
>>>>   lib/librte_vhost/vhost_user.h |  4 +++-
>>>>   3 files changed, 24 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
>>>> index d63031747..3b0287a26 100644
>>>> --- a/lib/librte_vhost/socket.c
>>>> +++ b/lib/librte_vhost/socket.c
>>>> @@ -94,18 +94,24 @@ static struct vhost_user vhost_user = {
>>>>       .mutex = PTHREAD_MUTEX_INITIALIZER,
>>>>   };
>>>> -/* return bytes# of read on success or negative val on failure. */
>>>> +/*
>>>> + * return bytes# of read on success or negative val on failure. 
>>>> Update fdnum
>>>> + * with number of fds read.
>>>> + */
>>>>   int
>>>> -read_fd_message(int sockfd, char *buf, int buflen, int *fds, int 
>>>> fd_num)
>>>> +read_fd_message(int sockfd, char *buf, int buflen, int *fds, int 
>>>> max_fds,
>>>> +        int *fd_num)
>>>>   {
>>>>       struct iovec iov;
>>>>       struct msghdr msgh;
>>>> -    size_t fdsize = fd_num * sizeof(int);
>>>> -    char control[CMSG_SPACE(fdsize)];
>>>> +    char control[CMSG_SPACE(max_fds * sizeof(int))];
>>>>       struct cmsghdr *cmsg;
>>>>       int got_fds = 0;
>>>> +    int *tmp_fds;
>>>>       int ret;
>>>> +    *fd_num = 0;
>>>> +
>>>>       memset(&msgh, 0, sizeof(msgh));
>>>>       iov.iov_base = buf;
>>>>       iov.iov_len  = buflen;
>>>> @@ -131,13 +137,22 @@ read_fd_message(int sockfd, char *buf, int 
>>>> buflen, int *fds, int fd_num)
>>>>           if ((cmsg->cmsg_level == SOL_SOCKET) &&
>>>>               (cmsg->cmsg_type == SCM_RIGHTS)) {
>>>>               got_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
>>>> +            if (got_fds > max_fds) {
>>>
>>> Hmm. I just noticed that 'msg_controllen' is set to receive
>>> not more than max_fds descriptors. So, this case should not
>>> be possible. We will receive MSG_CTRUNC and return before
>>> the loop.
>>
>> Maybe it is better to remove check for MSG_CTRUNC.
> s/remove/rework/
> 
>> IIUC, if MSG_CTRUNC happens, we may have to close anyway the ones
>> received.
>>
>> Do you agree?

So it seems that other use of MSG_CTRUNC in DPDK and QEMU does care
to close the ones that would have been received and just return an
error.

I propose to do the same for now, an remove the got_fds > max_fds part.

>>> +                RTE_LOG(ERR, VHOST_CONFIG,
>>>> +                    "Received msg contains more fds than 
>>>> supported\n");
>>>> +                tmp_fds = (int *)CMSG_DATA(cmsg);
>>>> +                while (got_fds--)
>>>> +                    close(tmp_fds[got_fds]);
>>>> +                return -1;
>>>> +            }
>>>> +            *fd_num = got_fds;
>>>>               memcpy(fds, CMSG_DATA(cmsg), got_fds * sizeof(int));
>>>>               break;
>>>>           }
>>>>       }
>>>>       /* Clear out unused file descriptors */
>>>> -    while (got_fds < fd_num)
>>>> +    while (got_fds < max_fds)
>>>>           fds[got_fds++] = -1;
>>>>       return ret;
>>>> diff --git a/lib/librte_vhost/vhost_user.c 
>>>> b/lib/librte_vhost/vhost_user.c
>>>> index 83d3e6321..c1c5f35ff 100644
>>>> --- a/lib/librte_vhost/vhost_user.c
>>>> +++ b/lib/librte_vhost/vhost_user.c
>>>> @@ -1509,7 +1509,7 @@ read_vhost_message(int sockfd, struct 
>>>> VhostUserMsg *msg)
>>>>       int ret;
>>>>       ret = read_fd_message(sockfd, (char *)msg, VHOST_USER_HDR_SIZE,
>>>> -        msg->fds, VHOST_MEMORY_MAX_NREGIONS);
>>>> +        msg->fds, VHOST_MEMORY_MAX_NREGIONS, &msg->fd_num);
>>>>       if (ret <= 0)
>>>>           return ret;
>>>> diff --git a/lib/librte_vhost/vhost_user.h 
>>>> b/lib/librte_vhost/vhost_user.h
>>>> index 62654f736..9a91d496b 100644
>>>> --- a/lib/librte_vhost/vhost_user.h
>>>> +++ b/lib/librte_vhost/vhost_user.h
>>>> @@ -132,6 +132,7 @@ typedef struct VhostUserMsg {
>>>>           VhostUserVringArea area;
>>>>       } payload;
>>>>       int fds[VHOST_MEMORY_MAX_NREGIONS];
>>>> +    int fd_num;
>>>>   } __attribute((packed)) VhostUserMsg;
>>>>   #define VHOST_USER_HDR_SIZE offsetof(VhostUserMsg, payload.u64)
>>>> @@ -155,7 +156,8 @@ int vhost_user_iotlb_miss(struct virtio_net 
>>>> *dev, uint64_t iova, uint8_t perm);
>>>>   int vhost_user_host_notifier_ctrl(int vid, bool enable);
>>>>   /* socket.c */
>>>> -int read_fd_message(int sockfd, char *buf, int buflen, int *fds, 
>>>> int fd_num);
>>>> +int read_fd_message(int sockfd, char *buf, int buflen, int *fds, 
>>>> int max_fds,
>>>> +        int *fd_num);
>>>>   int send_fd_message(int sockfd, char *buf, int buflen, int *fds, 
>>>> int fd_num);
>>>>   #endif
>>>>